1. Field of the Invention
The present invention relates to a method and an apparatus for the execution of a program by a program-controlled device.
2. Description of the Background Art
Program-controlled devices of this type may be designed for example as a microprocessor, microcontroller, signal processor or the like. The construction of such program-controlled devices has been known in many cases in innumerable embodiments for many years, and so it will not be discussed in any greater detail. A processor will generally be assumed hereinafter as an example of a program-controlled device.
Every processor has its own instruction set, the scope of which is predefined by an available bit width for instructions of the processor. If the bit width for instructions is two bits, for example, then a maximum of four different instructions are available to the corresponding processor.
Therefore, extending the instruction set of a processor generally also requires increasing the bit width provided for instructions, the so-called instruction bit width, unless the available instruction space of the processor is not yet fully exhausted. This latter may occur for example in the case of complex microprocessors having a large instruction bit width.
However, if the instruction space is fully exhausted, then it is not possible to implement the functionality of a processor only by extending the instruction scope without a circuitry intervention in the integrated circuit of the processor. Such circuitry changes exhibit inherent serious disadvantages, however, e.g., they are usually also accompanied by an enlargement of the chip area of the processor, a result of which being that the integrated circuit representing the processor is significantly more expensive to produce. This is at contrary with endeavoring to produce integrated circuits and corresponding processors smaller and smaller and thus ever more cost-effectively.
Moreover, interventions in the circuitry of a processor also always entail the risk of errors creeping in, which risk reduces the design security and which errors usually have to be eliminated in a very complicated manner. This is the case particularly with optimized processors, which have not been exclusively developed by automatic development tools for the chip design, but rather have been optimized as if it were “manually”.
In order to avoid the limitations outlined above, and the associated disadvantages, the functionality of an integrated circuit, which has hitherto been provided by hardware elements such as processors or corresponding electronic circuit, is increasingly being moved into the program or the software of the corresponding hardware or of the processor.
In the case of smaller circuit arrangements or devices such as programmable transponders, for example, this constitutes a significant problem, because their chip areas and thus also the memory space available for software are very limited. Such programmable transponders are also referred to as a “tag” since they are often used as if they were markers or labels for identifying products. A programmable transponder or tag typically includes a microchip and a transmitting/receiving antenna through which data can be interchanged, for example, with base stations bidirectionally by radio.
However, the radio transmission link used for data transmission between the base station and the transponder is of a very narrowband nature. Moreover, the transmission times are very limited temporally.
In order to be able to comply with these boundary conditions, the processors used for such programmable transponders have instruction sets having a very small bit width of merely two bits, for example. The four different instructions available as a result of this have regularly already been allocated, so that an intervention in the integrated circuit of the transponder is necessary for the implementation of at least one additional instruction. Without such a circuitry change, it is not possible to implement at least one additional instruction in the case of currently available transponders having a small bit width. This is a state of affairs which, understandably, should be avoided.